1. Field of the Invention
The invention relates to a device for subjecting air to UV(C) radiation, which device comprises:
a housing with an air inlet and an air outlet;
a UV(C) treatment chamber which is present in the housing and in which is accommodated a UV(C) source which subjects the passing air to a UV(C) treatment, the effectiveness of which depends on the intensity of the UV(C) radiation and on the residence time of the air in the UV(C) treatment chamber;
measuring means for measuring the value of at least one parameter representative of this intensity and for generating a measurement signal corresponding with this value to an external processor, in which a process window is stored which indicates the limits of the process effectiveness and the corresponding limits of the intensity and the residence time;
which measuring means comprise at least one of the following measuring units:
(a) a temperature sensor which measures the temperature on the wall of the UV(C) source;
(b) two temperature sensors which are placed respectively downstream and upstream relative to the UV(C) source in order to determine the heating of the passing air caused by the UV(C) source;
(c) a UV(C) sensor for determining the intensity of the UV(C) radiation at a selected position in the UV(C) treatment chamber;
which UV(C) source comprises at least one UV(C) lamp which is held by a lamp holder, which comprises terminal openings into which electrical terminal pins protruding from the or each UV(C) lamp can be inserted, which terminal openings are connected to electrical supply wires with respective insulating sheaths, which electrical supply wires can be connected with their free ends to an electric power supply unit; and
which measuring means are connected to electric signal wires with respective insulating sheaths, which electrical signal wires can be connected with their free ends to the external processor.
Such a device is known from international patent application WO-A-2005/039659 of applicant.
2. Discussion of Background Information
It is known that many physical, biological and biophysical processes are subjected to influencing factors which can often be expressed in terms of change in the values of relevant process parameters. To enable such a process to be controlled in the desired manner, in particular to keep the process confined within a defined process window, it is essential that relevant parameters are measured and, on the basis thereof, these parameters and/or other related parameters are continuously adjusted in dynamic manner. In the case where the process shifts outside a process window it is thus possible to intervene on the basis of the relevant measurement data, so that the process can be brought once again within the process window on the basis of new settings of one or more parameters.
As the process window becomes narrower, i.e. is determined within values that are closer together, the more accurate the measurements must be.
In the present case of a device intended for sterilization of air there are physical and biophysical processes which have a common factor, i.e. the time, expressed in seconds, and a related flow rate of the air flowing through the device. In order to be able to control such a process in the desired manner a reliable measurement of, among other quantities, the flow rate of the throughflow air is therefore necessary. A flow rate measurement can be performed by determining the (average) air speed at a given throughflow area.
Diverse methods exist for measuring air speed. Several examples thereof are described briefly hereinbelow.
(A) A so-called vane-anemometer comprises a propeller with precisely known aerodynamic properties which is driven by throughflow air. The propeller is placed in the airflow and, for instance by making use of an optical sensor, the rotation speed of the propeller is measured. The frequency of the propeller or the rotation speed is converted via a calibration table into an electrical signal which is representative of the air speed.
(B) A hot-wire anemometer makes use of a wire of resistance material through which an electric current is passed. The wire is heated by the electric current running therethrough and obtains an initial surface temperature at an air flow rate with the value zero. When air then begins to flow therealong, a heat transfer will take place between the wire and the passing air. As a result the wire will cool, which is expressed in a changing resistance value. An electrical measuring and control circuit then transmits a stronger current through the wire, until the initial temperature has once more been reached. The increase in the current or in the power fed to the wire in the dynamic situation relative to the static situation can then be converted to a value of the air speed.
(C) Manometers can also determine the air speed on the basis of a pressure difference between two measuring points.
(D) A further possibility is the use of venturi means.